Prefrontal stimulation of [GABA.sub.A] receptors counteracts the corticolimbic hyperactivity produced by NMDA antagonists in the prefrontal cortex of the rat

• Published in: Psychopharmacology Vol. 214; no. 2; p. 525
• Main Authors: Del Arco, Alberto, Ronzoni, Giacomo, Mora, Francisco
• Format: Journal Article
• Language: English
• Published: Springer 15-03-2011
• Subjects: Acetylcholine; Computer industry; Corticosterone; GABA; Methyl aspartate; United States; Spain
• ISSN: 0033-3158
• DOI: 10.1007/s00213-010-2055-9

Rationale The hypofunction of NMDA receptors in the prefrontal cortex (PFC) has been suggested to produce corticolimbic hyperactivity through the reduction of cortical GABA transmission. Objectives The present study investigates the effects of injections of the NMDA antagonist 3-[(R)-2-carboxypiperazin4-yl]-propyl-1-phosphonic acid (CPP) into the PFC on (1) the release of dopamine and/or acetylcholine in the amygdala and hippocampus, (2) the levels of corticosterone in the hippocampus and (3) spontaneous motor activity. Also, the stimulation of [GABA.sub.A] receptors, by prefrontal injections of muscimol, on the effects produced by NMDA antagonists on these same neurochemical, hormonal and behavioural parameters was evaluated. Methods Male Wistar rats were implanted with guide cannulae to perform bilateral microinjections into the PFC and microdialysis experiments in the amygdala and/or ventral hippocampus, simultaneously. Spontaneous motor activity was monitored in the open field. Results Injections of CPP (1 µg/0.5 µl) into the PFC increased dialysate concentrations of dopamine and acetylcholine in the amygdala, acetylcholine and free corticosterone in the hippocampus and also motor activity. Simultaneous injections of muscimol (0.5 µg/0.5 µl) into the PFC counteracted the increases of dopamine and acetylcholine in the amygdala and hippocampus and also significantly reduced the peak increase of corticosterone in the hippocampus. Injections of muscimol (0.05 and 0.5 µg 0.5 µl) reduced the increases of motor activity produced by prefrontal NMDA antagonists. Conclusions These results suggest that the hypofunction of NMDA receptors in the PFC produces corticolimbic hyperactivity through the activation of prefrontal efferent projections to subcortical/limbic areas. Keywords NMDA receptor * GABA receptor. Dopamine * Acetylcholine * Corticosterone * Prefrontal cortex * Amygdala * Hippocampus * Motor activity * Rat * Schizophrenia